1. Field of the Invention
This invention relates to a glass-fiber reinforced polypropylene resin composition having high stiffness, superior high-impact properties and high molding fluidity.
2. Related Art Statement
Glass-fiber reinforced polypropylene resins have superior stiffness, heat resistance, etc. to those of usual polypropylene resins; hence they have so far been broadly used for various industrial parts including automobile parts, electrical parts, etc.
However, in order to produce glass-fiber reinforced polypropylene resin compositions, even if crystalline polypropylene and glass fibers are merely melt-kneaded together, no sufficient reinforcement is effected since adhesion of polypropylene resin to glass fibers is weak due to non-polarity of polypropylene. Further, when glass fibers are added to polypropylene resin and the latter is melted, its fluidity generally lowers, and it is the present status that particularly when the blend is molded into a large size of molded products, such molding is often restricted in the aspect of molding machine, molding conditions, mold design, etc.
As processes for improving the adhesion between polypropylene resin and glass fibers, various processes have been proposed such as a process of adding surface-treated glass fibers to a polypropylene modified with a carboxylic acid, a carboxylic acid anhydride or an unsaturated carboxylic acid (Japanese patent publication No. Sho 49-49029/1974 USP 4003874), a process of blending glass fibers and a modified polypropylene modified with an unsaturated carboxylic acid according to solution method, with a polypropylene resin (Japanese patent publication No. Sho 54-44696/1979), etc. However, any of these processes have been confirmed to have an effectiveness of improving the stiffness and high-impact properties, but they are insufficient to satisfy well-balanced mechanical physical properties required by the current market.
Further, in addition to the above processes, a composition having an improved molding fluidity has been proposed (Japanese patent application laid-open No. Sho 57-182343/1982), but this is also not practical since the kind of polypropylene resins used is limited.
Besides, a process of melt-kneading a polyolefin, glass fibers, an unsaturated silane compound, an organic carboxylic acid and a radical-generating agent has also been proposed, but although the composition obtained according to such a process is advantageous in the aspect of cost, the composition has coloring and odor and also is low in the effectiveness of improving the stiffness and high-impact properties.